Stay Alive Capacitors

[DEREK123]

Hi

Is there any benefit in using 2 off  DCCconcept DCD-ZNSA1 instead of just 1 when installing decoders , I have  3 LAIS decoders ( they seem to work with them ok ) ?

I am no electronics man but the guy in the shop says that using 2 will give better stay alive performance across points which is where my 0-6-0 locos hesitate. .

Thanks

Derek

[Chrissaf]

A 'Stay Alive' is basically a capacitor component. Buying a 'Stay Alive' as a ready made commercial product is a very expensive way of obtaining stay alive components. However that said, a capacitor stores an electrical charge (think of it as like a small battery that runs down very quickly). The time it takes for the capacitor to run down can be increased by increasing its Farad value. Farads are what capacitor values are defined by. If you connect two or more capacitors in parallel, then their Farad values are mathmatically added together. So in conclusion, connecting two 'Stay Alives' of the SAME value together in parallel, will double its overall power storage capacity. It will also increase the 'in rush' current, so this should be considered to.

[Howbi]

When the capacitors are connected in parallel then the total capacitance will equal their sum........so two 1000uF in parallel will give a total of 2000uF........however, is there enough room for two?.........one larger capacity capacitor could be a better option.........I would query the actual capacitance of the DCD-ZNSA1 because if it isn't of sufficient capacity it will be a waste of time and money........your need at least 2200uF to have any meaningful effect IMHO......HB

[DEREK123]

Thanks Chris ...

One more silly question .... I have 2 dark blue wires trailing from the decoder .... how should I wire them up to 2 capacitors ? ... I'm not very sure about parallel and in seriies wiring !!

I appreciate your help.

Derek

 

Thanks too HB ... ships passing in the dark !!!!

[DEREK123]

HB ... soory we passed !!

I am currently converting an old Princess Eliz.. Tender to hold the bits ... it works okay the Loco

is an R52 Jinty ( A really nice one ).

I will check out the actual capacitance of the DCD-ZNSA1 as soon as I can and report back once I know.

Cheers

Derek

[Fishmanoz]

You might also have a look at https://www.hornby.com/uk-en/forum/tcs-keep-alive/ and do a forum search on keep alive in post content. These use much higher value super capacitors and née additional components to control them,  no problem to fit it all in your tender. 

 

And if if you look up the decoder specs on the web site, it will tell you which wire does what. In parallel means you join the capacitor wires to each other at each end, making sure the polarity matches. In series, you just join one end of each and the other 2 wires connect to your circuit. 

[DEREK123]

Hi Fishmanoz ... I thank you that is most useful.

In my earlier reply above I said 2 blue wires that is wrong !! ... I should have said 1 Blue and 1 Black ... ( Whoops !! )

So far I have been unable to find the farad value of the concepts capacitor .... DCC Concepts website just says high powered !! .... can the component be measured ?

Derek

[Chrissaf]

Capacitors used in Stay Alives have polarity, which means that they have a positive and a negative side. If you connect them the wrong way round the capacitor will swell up and could potentially go off with a bang. The blue wire from the decoder is usually the positive wire and the black wire negative. Positive wire (blue) to capacitor positive and negative wire (black) to capacitor negative.

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I am not surprised that DCC concepts do not publish the capacitor values or internal circuit of their 'Stay Alives'. If they did, then it would be easy to see how much you are being over-charged for such basic everyday cheap components, and how easy it would be to make your own. Super capacitors are physically smaller and need additional components when used in a Stay Alive. The circuit details of parallel versus series wiring and construction of Stay Alives using super capacitors are in this previous post (look at my multiple replies in this thread linked below).

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https://www.hornby.com/uk-en/forum/post/view/topic_id/13404/?p=2

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You need specialist tools to measure the Farad value of a capacitor. My meter only measures capacitors up to a max of 200uF (0.002 Farads), so you would need Industry quality measuring instruments to measure capacitor values in the multi-thousands range.

[DEREK123]

Hi Chris  

Thankfully I have not fitted one yet !! .... I would most likely got it wrong ..... know my luck !  ☹️

Derek

[aas]

how do you wire a stayalive to a tts decoder      regards   aas

[Chrissaf]

@aas

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The TTS decoder is very similar to Hornby's standard R8249 decoder. Look at the thread linked to in my last post above. It has the Stay Alive connection details for a Hornby R8249. The principle of finding the negative side of the rectifier bridge (to which to connect the negative side of the Stay Alive capacitor) is a principle, common across most loco decoders. The positive side connection of the Stay Alive is not normally an issue as any multi-function decoder will normally have the positive wire (blue) extended from the decoder.

[Howbi]

Here's one I made earlier.......the original cap on the decoder was only 470uF, pretty useless so I fitted a larger 2200uF instead........this works very well.........snag is that this cap is of a size that will not find adequate space in many 0-6-0 locos and it these smaller tanks that benefit most from the stay-alive........HB

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[2e0dtoeric]

You should really have taken the heat-shrink right up to the cap's body - not left bare wires protruding! Short-circuits are just an explosion waiting to happen!  😛

[Howbi]

Thanks, Eric, duly noted......... 😳.........HB

[DEREK123]

Hi HB & Eric

Looks good and something that I am capable of doing  HB !! ....... are the + & - marks marked on the capacitor ?

What do I ask for when I buy ? ( Will I get it in Maplins ? )

( That's a great tip Eric.) 

Thanks guys ... saves me dicing with parallel / series too !! 

Derek

[Chrissaf]

Electrolytic (can) capacitors have a short leg (negative) and a long leg (positive). The short negative leg is also positioned next to a strip marked with " - - - - - - "  [a number of minus symbols] printed on the plastic can coating. The positive and negative connection will be completely self evident to you when you have the capacitor in your hand in front of you.

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Note there are two types of Electrolytic capacitors, the type I have described above is one type. The other type is called an Axial Electrolytic. The Axial has a connection wire at each end of the capacitor (as opposed to both wires coming out of the same end). With an Axial Electrolytic capacitor, the positive lead is at the end of the capacitor that has the ridge in the casing.

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The only good thing to say about Maplin is that they are handy being in the high street if you need a component urgently over the counter. Personally I buy my components from on-line suppliers of which there are loads to choose from, plus good old 'from China via eBay' suppliers.

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In terms of which one. Search for an Electrolytic capacitor. Basically the largest uF (micro-Farad) value you can get that is physically small enough to fit in the space available. It also needs to be rated at 16 volts absolute minimum, but a 25 volt rating would be preferred IMO to provide a bit of a safety margin. The problem is that the higher voltage rating means a physically bigger capacitor for the same uF value.

[Howbi]

Derek123......just to add to Chris's post, this website has a comprehensive range of caps in stock and conveniently shows the dimensions of each value which will be significant in trying to fit into smaller locos.....

https://www.technobotsonline.com/85-deg-c-electrolytic-radial-capacitors.html

[DEREK123]

Hi Chris and HB

 

BRILLIANT !! ... You are both stars. !!!

Cheers

Derek

[Chrissaf]

Derek, on HB's site, just for clarity when looking at the quoted dimensions. The third number marked "pitch" can be largely ignored. The "pitch" is the distance measured between the two connecting leads (useful if mounting the capacitor on a PCB). The first and second numbers are the important ones, the length and diameter of the capacitor in mm.

[DEREK123]

ProductPart No.QuantityUnit priceSubtotalRadial Electrolytic Capacitor 2200uF 16V2017-0225£0.29£1.45 

Chris / HB

This is the capacitor I have ordered ( from HB's technobotsonline ) . Is it the right one?

(  Size should be fine for my loco. )

Cheers

Derek

[Chrissaf]

It is suitable....along as you say that it is small enough to fit the space available.

[DEREK123]

Hi Chris

Thanks for that.

Derek

[aas]

not very good with technical need a diagram if posible please on where the wires fit on a tts decoder  for stayalive   regards     aas

[Chrissaf]

In that case, I would advise against you trying to do this mod yourself. The area on the decoder to where the wires need to be soldered are tiny and you need a very fine tipped soldering iron, good eyesight and a very steady hand.

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I have already provided a diagram for a very similar decoder. The clickable link to it is on the third post up from the bottom on page 1 of this thread.

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If you have a TTS decoder (I haven't) then post a close up photo of BOTH sides of the decoder PCB, and I will see if I can identify the connection positions for you.

[aas]

thankyou chris        i have a small soldering iron  and a magnifying glass    regards aas